vt8500_serial.c

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/*
 * Copyright (C) 2010 Alexey Charkov <[email protected]>
 *
 * Based on msm_serial.c, which is:
 * Copyright (C) 2007 Google, Inc.
 * Author: Robert Love <[email protected]>
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#if defined(CONFIG_SERIAL_VT8500_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
# define SUPPORT_SYSRQ
#endif

#include <linux/hrtimer.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/irq.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/slab.h>
#include <linux/clk.h>
#include <linux/platform_device.h>
#include <linux/of.h>

/*
 * UART Register offsets
 */

#define VT8500_URTDR        0x0000  /* Transmit data */
#define VT8500_URRDR        0x0004  /* Receive data */
#define VT8500_URDIV        0x0008  /* Clock/Baud rate divisor */
#define VT8500_URLCR        0x000C  /* Line control */
#define VT8500_URICR        0x0010  /* IrDA control */
#define VT8500_URIER        0x0014  /* Interrupt enable */
#define VT8500_URISR        0x0018  /* Interrupt status */
#define VT8500_URUSR        0x001c  /* UART status */
#define VT8500_URFCR        0x0020  /* FIFO control */
#define VT8500_URFIDX       0x0024  /* FIFO index */
#define VT8500_URBKR        0x0028  /* Break signal count */
#define VT8500_URTOD        0x002c  /* Time out divisor */
#define VT8500_TXFIFO       0x1000  /* Transmit FIFO (16x8) */
#define VT8500_RXFIFO       0x1020  /* Receive FIFO (16x10) */

/*
 * Interrupt enable and status bits
 */

#define TXDE    (1 << 0)    /* Tx Data empty */
#define RXDF    (1 << 1)    /* Rx Data full */
#define TXFAE   (1 << 2)    /* Tx FIFO almost empty */
#define TXFE    (1 << 3)    /* Tx FIFO empty */
#define RXFAF   (1 << 4)    /* Rx FIFO almost full */
#define RXFF    (1 << 5)    /* Rx FIFO full */
#define TXUDR   (1 << 6)    /* Tx underrun */
#define RXOVER  (1 << 7)    /* Rx overrun */
#define PER (1 << 8)    /* Parity error */
#define FER (1 << 9)    /* Frame error */
#define TCTS    (1 << 10)   /* Toggle of CTS */
#define RXTOUT  (1 << 11)   /* Rx timeout */
#define BKDONE  (1 << 12)   /* Break signal done */
#define ERR (1 << 13)   /* AHB error response */

#define RX_FIFO_INTS    (RXFAF | RXFF | RXOVER | PER | FER | RXTOUT)
#define TX_FIFO_INTS    (TXFAE | TXFE | TXUDR)

#define VT8500_MAX_PORTS    6

struct vt8500_port {
    struct uart_port    uart;
    char            name[16];
    struct clk      *clk;
    unsigned int        ier;
};

/*
 * we use this variable to keep track of which ports
 * have been allocated as we can't use pdev->id in
 * devicetree
 */
static unsigned long vt8500_ports_in_use;

static inline void vt8500_write(struct uart_port *port, unsigned int val,
                 unsigned int off)
{
    writel(val, port->membase + off);
}

static inline unsigned int vt8500_read(struct uart_port *port, unsigned int off)
{
    return readl(port->membase + off);
}

static void vt8500_stop_tx(struct uart_port *port)
{
    struct vt8500_port *vt8500_port = container_of(port,
                               struct vt8500_port,
                               uart);

    vt8500_port->ier &= ~TX_FIFO_INTS;
    vt8500_write(port, vt8500_port->ier, VT8500_URIER);
}

static void vt8500_stop_rx(struct uart_port *port)
{
    struct vt8500_port *vt8500_port = container_of(port,
                               struct vt8500_port,
                               uart);

    vt8500_port->ier &= ~RX_FIFO_INTS;
    vt8500_write(port, vt8500_port->ier, VT8500_URIER);
}

static void vt8500_enable_ms(struct uart_port *port)
{
    struct vt8500_port *vt8500_port = container_of(port,
                               struct vt8500_port,
                               uart);

    vt8500_port->ier |= TCTS;
    vt8500_write(port, vt8500_port->ier, VT8500_URIER);
}

static void handle_rx(struct uart_port *port)
{
    struct tty_struct *tty = tty_port_tty_get(&port->state->port);
    if (!tty) {
        /* Discard data: no tty available */
        int count = (vt8500_read(port, VT8500_URFIDX) & 0x1f00) >> 8;
        u16 ch;
        while (count--)
            ch = readw(port->membase + VT8500_RXFIFO);
        return;
    }

    /*
     * Handle overrun
     */
    if ((vt8500_read(port, VT8500_URISR) & RXOVER)) {
        port->icount.overrun++;
        tty_insert_flip_char(tty, 0, TTY_OVERRUN);
    }

    /* and now the main RX loop */
    while (vt8500_read(port, VT8500_URFIDX) & 0x1f00) {
        unsigned int c;
        char flag = TTY_NORMAL;

        c = readw(port->membase + VT8500_RXFIFO) & 0x3ff;

        /* Mask conditions we're ignorning. */
        c &= ~port->read_status_mask;

        if (c & FER) {
            port->icount.frame++;
            flag = TTY_FRAME;
        } else if (c & PER) {
            port->icount.parity++;
            flag = TTY_PARITY;
        }
        port->icount.rx++;

        if (!uart_handle_sysrq_char(port, c))
            tty_insert_flip_char(tty, c, flag);
    }

    tty_flip_buffer_push(tty);
    tty_kref_put(tty);
}

static void handle_tx(struct uart_port *port)
{
    struct circ_buf *xmit = &port->state->xmit;

    if (port->x_char) {
        writeb(port->x_char, port->membase + VT8500_TXFIFO);
        port->icount.tx++;
        port->x_char = 0;
    }
    if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
        vt8500_stop_tx(port);
        return;
    }

    while ((vt8500_read(port, VT8500_URFIDX) & 0x1f) < 16) {
        if (uart_circ_empty(xmit))
            break;

        writeb(xmit->buf[xmit->tail], port->membase + VT8500_TXFIFO);

        xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
        port->icount.tx++;
    }

    if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
        uart_write_wakeup(port);

    if (uart_circ_empty(xmit))
        vt8500_stop_tx(port);
}

static void vt8500_start_tx(struct uart_port *port)
{
    struct vt8500_port *vt8500_port = container_of(port,
                               struct vt8500_port,
                               uart);

    vt8500_port->ier &= ~TX_FIFO_INTS;
    vt8500_write(port, vt8500_port->ier, VT8500_URIER);
    handle_tx(port);
    vt8500_port->ier |= TX_FIFO_INTS;
    vt8500_write(port, vt8500_port->ier, VT8500_URIER);
}

static void handle_delta_cts(struct uart_port *port)
{
    port->icount.cts++;
    wake_up_interruptible(&port->state->port.delta_msr_wait);
}

static irqreturn_t vt8500_irq(int irq, void *dev_id)
{
    struct uart_port *port = dev_id;
    unsigned long isr;

    spin_lock(&port->lock);
    isr = vt8500_read(port, VT8500_URISR);

    /* Acknowledge active status bits */
    vt8500_write(port, isr, VT8500_URISR);

    if (isr & RX_FIFO_INTS)
        handle_rx(port);
    if (isr & TX_FIFO_INTS)
        handle_tx(port);
    if (isr & TCTS)
        handle_delta_cts(port);

    spin_unlock(&port->lock);

    return IRQ_HANDLED;
}

static unsigned int vt8500_tx_empty(struct uart_port *port)
{
    return (vt8500_read(port, VT8500_URFIDX) & 0x1f) < 16 ?
                        TIOCSER_TEMT : 0;
}

static unsigned int vt8500_get_mctrl(struct uart_port *port)
{
    unsigned int usr;

    usr = vt8500_read(port, VT8500_URUSR);
    if (usr & (1 << 4))
        return TIOCM_CTS;
    else
        return 0;
}

static void vt8500_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
}

static void vt8500_break_ctl(struct uart_port *port, int break_ctl)
{
    if (break_ctl)
        vt8500_write(port, vt8500_read(port, VT8500_URLCR) | (1 << 9),
                 VT8500_URLCR);
}

static int vt8500_set_baud_rate(struct uart_port *port, unsigned int baud)
{
    unsigned long div;
    unsigned int loops = 1000;

    div = vt8500_read(port, VT8500_URDIV) & ~(0x3ff);

    if (unlikely((baud < 900) || (baud > 921600)))
        div |= 7;
    else
        div |= (921600 / baud) - 1;

    while ((vt8500_read(port, VT8500_URUSR) & (1 << 5)) && --loops)
        cpu_relax();
    vt8500_write(port, div, VT8500_URDIV);

    return baud;
}

static int vt8500_startup(struct uart_port *port)
{
    struct vt8500_port *vt8500_port =
            container_of(port, struct vt8500_port, uart);
    int ret;

    snprintf(vt8500_port->name, sizeof(vt8500_port->name),
         "vt8500_serial%d", port->line);

    ret = request_irq(port->irq, vt8500_irq, IRQF_TRIGGER_HIGH,
              vt8500_port->name, port);
    if (unlikely(ret))
        return ret;

    vt8500_write(port, 0x03, VT8500_URLCR); /* enable TX & RX */

    return 0;
}

static void vt8500_shutdown(struct uart_port *port)
{
    struct vt8500_port *vt8500_port =
            container_of(port, struct vt8500_port, uart);

    vt8500_port->ier = 0;

    /* disable interrupts and FIFOs */
    vt8500_write(&vt8500_port->uart, 0, VT8500_URIER);
    vt8500_write(&vt8500_port->uart, 0x880, VT8500_URFCR);
    free_irq(port->irq, port);
}

static void vt8500_set_termios(struct uart_port *port,
                   struct ktermios *termios,
                   struct ktermios *old)
{
    struct vt8500_port *vt8500_port =
            container_of(port, struct vt8500_port, uart);
    unsigned long flags;
    unsigned int baud, lcr;
    unsigned int loops = 1000;

    spin_lock_irqsave(&port->lock, flags);

    /* calculate and set baud rate */
    baud = uart_get_baud_rate(port, termios, old, 900, 921600);
    baud = vt8500_set_baud_rate(port, baud);
    if (tty_termios_baud_rate(termios))
        tty_termios_encode_baud_rate(termios, baud, baud);

    /* calculate parity */
    lcr = vt8500_read(&vt8500_port->uart, VT8500_URLCR);
    lcr &= ~((1 << 5) | (1 << 4));
    if (termios->c_cflag & PARENB) {
        lcr |= (1 << 4);
        termios->c_cflag &= ~CMSPAR;
        if (termios->c_cflag & PARODD)
            lcr |= (1 << 5);
    }

    /* calculate bits per char */
    lcr &= ~(1 << 2);
    switch (termios->c_cflag & CSIZE) {
    case CS7:
        break;
    case CS8:
    default:
        lcr |= (1 << 2);
        termios->c_cflag &= ~CSIZE;
        termios->c_cflag |= CS8;
        break;
    }

    /* calculate stop bits */
    lcr &= ~(1 << 3);
    if (termios->c_cflag & CSTOPB)
        lcr |= (1 << 3);

    /* set parity, bits per char, and stop bit */
    vt8500_write(&vt8500_port->uart, lcr, VT8500_URLCR);

    /* Configure status bits to ignore based on termio flags. */
    port->read_status_mask = 0;
    if (termios->c_iflag & IGNPAR)
        port->read_status_mask = FER | PER;

    uart_update_timeout(port, termios->c_cflag, baud);

    /* Reset FIFOs */
    vt8500_write(&vt8500_port->uart, 0x88c, VT8500_URFCR);
    while ((vt8500_read(&vt8500_port->uart, VT8500_URFCR) & 0xc)
                            && --loops)
        cpu_relax();

    /* Every possible FIFO-related interrupt */
    vt8500_port->ier = RX_FIFO_INTS | TX_FIFO_INTS;

    /*
     * CTS flow control
     */
    if (UART_ENABLE_MS(&vt8500_port->uart, termios->c_cflag))
        vt8500_port->ier |= TCTS;

    vt8500_write(&vt8500_port->uart, 0x881, VT8500_URFCR);
    vt8500_write(&vt8500_port->uart, vt8500_port->ier, VT8500_URIER);

    spin_unlock_irqrestore(&port->lock, flags);
}

static const char *vt8500_type(struct uart_port *port)
{
    struct vt8500_port *vt8500_port =
            container_of(port, struct vt8500_port, uart);
    return vt8500_port->name;
}

static void vt8500_release_port(struct uart_port *port)
{
}

static int vt8500_request_port(struct uart_port *port)
{
    return 0;
}

static void vt8500_config_port(struct uart_port *port, int flags)
{
    port->type = PORT_VT8500;
}

static int vt8500_verify_port(struct uart_port *port,
                  struct serial_struct *ser)
{
    if (unlikely(ser->type != PORT_UNKNOWN && ser->type != PORT_VT8500))
        return -EINVAL;
    if (unlikely(port->irq != ser->irq))
        return -EINVAL;
    return 0;
}

static struct vt8500_port *vt8500_uart_ports[VT8500_MAX_PORTS];
static struct uart_driver vt8500_uart_driver;

#ifdef CONFIG_SERIAL_VT8500_CONSOLE

static inline void wait_for_xmitr(struct uart_port *port)
{
    unsigned int status, tmout = 10000;

    /* Wait up to 10ms for the character(s) to be sent. */
    do {
        status = vt8500_read(port, VT8500_URFIDX);

        if (--tmout == 0)
            break;
        udelay(1);
    } while (status & 0x10);
}

static void vt8500_console_putchar(struct uart_port *port, int c)
{
    wait_for_xmitr(port);
    writeb(c, port->membase + VT8500_TXFIFO);
}

static void vt8500_console_write(struct console *co, const char *s,
                  unsigned int count)
{
    struct vt8500_port *vt8500_port = vt8500_uart_ports[co->index];
    unsigned long ier;

    BUG_ON(co->index < 0 || co->index >= vt8500_uart_driver.nr);

    ier = vt8500_read(&vt8500_port->uart, VT8500_URIER);
    vt8500_write(&vt8500_port->uart, VT8500_URIER, 0);

    uart_console_write(&vt8500_port->uart, s, count,
               vt8500_console_putchar);

    /*
     *  Finally, wait for transmitter to become empty
     *  and switch back to FIFO
     */
    wait_for_xmitr(&vt8500_port->uart);
    vt8500_write(&vt8500_port->uart, VT8500_URIER, ier);
}

static int __init vt8500_console_setup(struct console *co, char *options)
{
    struct vt8500_port *vt8500_port;
    int baud = 9600;
    int bits = 8;
    int parity = 'n';
    int flow = 'n';

    if (unlikely(co->index >= vt8500_uart_driver.nr || co->index < 0))
        return -ENXIO;

    vt8500_port = vt8500_uart_ports[co->index];

    if (!vt8500_port)
        return -ENODEV;

    if (options)
        uart_parse_options(options, &baud, &parity, &bits, &flow);

    return uart_set_options(&vt8500_port->uart,
                 co, baud, parity, bits, flow);
}

static struct console vt8500_console = {
    .name = "ttyWMT",
    .write = vt8500_console_write,
    .device = uart_console_device,
    .setup = vt8500_console_setup,
    .flags = CON_PRINTBUFFER,
    .index = -1,
    .data = &vt8500_uart_driver,
};

#define VT8500_CONSOLE  (&vt8500_console)

#else
#define VT8500_CONSOLE  NULL
#endif

static struct uart_ops vt8500_uart_pops = {
    .tx_empty   = vt8500_tx_empty,
    .set_mctrl  = vt8500_set_mctrl,
    .get_mctrl  = vt8500_get_mctrl,
    .stop_tx    = vt8500_stop_tx,
    .start_tx   = vt8500_start_tx,
    .stop_rx    = vt8500_stop_rx,
    .enable_ms  = vt8500_enable_ms,
    .break_ctl  = vt8500_break_ctl,
    .startup    = vt8500_startup,
    .shutdown   = vt8500_shutdown,
    .set_termios    = vt8500_set_termios,
    .type       = vt8500_type,
    .release_port   = vt8500_release_port,
    .request_port   = vt8500_request_port,
    .config_port    = vt8500_config_port,
    .verify_port    = vt8500_verify_port,
};

static struct uart_driver vt8500_uart_driver = {
    .owner      = THIS_MODULE,
    .driver_name    = "vt8500_serial",
    .dev_name   = "ttyWMT",
    .nr     = 6,
    .cons       = VT8500_CONSOLE,
};

static int __devinit vt8500_serial_probe(struct platform_device *pdev)
{
    struct vt8500_port *vt8500_port;
    struct resource *mmres, *irqres;
    struct device_node *np = pdev->dev.of_node;
    int ret;
    int port;

    mmres = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    irqres = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
    if (!mmres || !irqres)
        return -ENODEV;

    vt8500_port = kzalloc(sizeof(struct vt8500_port), GFP_KERNEL);
    if (!vt8500_port)
        return -ENOMEM;

    if (np)
        port = of_alias_get_id(np, "serial");
        if (port > VT8500_MAX_PORTS)
            port = -1;
    else
        port = -1;

    if (port < 0) {
        /* calculate the port id */
        port = find_first_zero_bit(&vt8500_ports_in_use,
                    sizeof(vt8500_ports_in_use));
    }

    if (port > VT8500_MAX_PORTS)
        return -ENODEV;

    /* reserve the port id */
    if (test_and_set_bit(port, &vt8500_ports_in_use)) {
        /* port already in use - shouldn't really happen */
        return -EBUSY;
    }

    vt8500_port->uart.type = PORT_VT8500;
    vt8500_port->uart.iotype = UPIO_MEM;
    vt8500_port->uart.mapbase = mmres->start;
    vt8500_port->uart.irq = irqres->start;
    vt8500_port->uart.fifosize = 16;
    vt8500_port->uart.ops = &vt8500_uart_pops;
    vt8500_port->uart.line = port;
    vt8500_port->uart.dev = &pdev->dev;
    vt8500_port->uart.flags = UPF_IOREMAP | UPF_BOOT_AUTOCONF;

    vt8500_port->clk = of_clk_get(pdev->dev.of_node, 0);
    if (vt8500_port->clk) {
        vt8500_port->uart.uartclk = clk_get_rate(vt8500_port->clk);
    } else {
        /* use the default of 24Mhz if not specified and warn */
        pr_warn("%s: serial clock source not specified\n", __func__);
        vt8500_port->uart.uartclk = 24000000;
    }

    snprintf(vt8500_port->name, sizeof(vt8500_port->name),
         "VT8500 UART%d", pdev->id);

    vt8500_port->uart.membase = ioremap(mmres->start, resource_size(mmres));
    if (!vt8500_port->uart.membase) {
        ret = -ENOMEM;
        goto err;
    }

    vt8500_uart_ports[port] = vt8500_port;

    uart_add_one_port(&vt8500_uart_driver, &vt8500_port->uart);

    platform_set_drvdata(pdev, vt8500_port);

    return 0;

err:
    kfree(vt8500_port);
    return ret;
}

static int __devexit vt8500_serial_remove(struct platform_device *pdev)
{
    struct vt8500_port *vt8500_port = platform_get_drvdata(pdev);

    platform_set_drvdata(pdev, NULL);
    uart_remove_one_port(&vt8500_uart_driver, &vt8500_port->uart);
    kfree(vt8500_port);

    return 0;
}

static const struct of_device_id wmt_dt_ids[] = {
    { .compatible = "via,vt8500-uart", },
    {}
};

static struct platform_driver vt8500_platform_driver = {
    .probe  = vt8500_serial_probe,
    .remove = __devexit_p(vt8500_serial_remove),
    .driver = {
        .name = "vt8500_serial",
        .owner = THIS_MODULE,
        .of_match_table = of_match_ptr(wmt_dt_ids),
    },
};

static int __init vt8500_serial_init(void)
{
    int ret;

    ret = uart_register_driver(&vt8500_uart_driver);
    if (unlikely(ret))
        return ret;

    ret = platform_driver_register(&vt8500_platform_driver);

    if (unlikely(ret))
        uart_unregister_driver(&vt8500_uart_driver);

    return ret;
}

static void __exit vt8500_serial_exit(void)
{
#ifdef CONFIG_SERIAL_VT8500_CONSOLE
    unregister_console(&vt8500_console);
#endif
    platform_driver_unregister(&vt8500_platform_driver);
    uart_unregister_driver(&vt8500_uart_driver);
}

module_init(vt8500_serial_init);
module_exit(vt8500_serial_exit);

MODULE_AUTHOR("Alexey Charkov <[email protected]>");
MODULE_DESCRIPTION("Driver for vt8500 serial device");
MODULE_LICENSE("GPL v2");